This invention relates to a grinding tool with a drive shaft and radial grinding elements.
There exist numerous grinding tools for machine-operated abrasive surface finishing. Examples of such traditional machines include rotary grinders employing a grinding medium in the form of a grinding sheet with an abrasive surface on a fabric, cellulose-based or plastic backing, radially extending from a motor-driven cylindrical base unit. The rotating tool is passed across the surface to be finished as the free ends of the grinding medium successively strike the surface and are moved across it. The tool may be part of an automatic system or it may be manually operated.
This conventional design is particularly useful when configured with a small tool diameter for finishing hard workpieces, for instance metal objects. When grinding workpieces of a soft material such as wood, there is always the danger of producing an uneven surface since the individual grinding elements attack the material at different force levels. This problem takes on increasingly significant proportions after the break-in period of the tool when due to usage the grinding elements have differently shaped ends. For finishing larger workpieces it becomes necessary to apply the grinder in machine-controlled fashion or to manually go over the entire surface repeatedly to cover the whole area, a process which is time-consuming and once again tends to pose a problem in achieving a homogeneous finish.
For larger workpieces the dimensions of the tool should be larger as well, especially with respect to its operating width. For conventional grinding tools, however, that would create major problems in terms of grinding performance since they would necessarily be quite stiff and inflexible over their width, making the grinding of non-planar, curved surfaces of a soft material virtually impossible.
The U.S. Pat. No. 3,869,833 describes a grinding tool with a drive shaft from which grinding elements, mounted on a carrier band, project radially outward. Each grinding element is attached to a retaining pin that is positioned at a distance from and parallel to the drive shaft. The retaining pins are spaced from one another and attached, along a circular path around the drive shaft, to a base unit.
It is the objective of this invention to introduce a grinding tool which is capable of also finishing workpieces of a soft material such as wood and having a curved surface.
According to the invention, this capability is provided by a grinding tool with the features per claim 1.
Other preferred design versions are characterized by the features described in the subordinated claims 2 to 11.
By virtue of the design of the grinding tool according to this invention, a tool is provided which, even when it is large or has a large working width, is capable of following curved contours as a well and indeed lends itself particularly well to the surfacing of workpieces of a soft material such as wood. It is an advantage of this design that it permits the tool to be relatively wide, i.e. with a large effective operating width, thus permitting even large, curved workpieces to be surface-finished in just a few steps. It is especially the surfaces of three-dimensionally cambered objects that can be finished quickly and in optimal fashion even when the workpiece consists of a soft material such as wood.
As an added benefit, the tool according to this invention is highly durable and is relatively easy to maintain.
While the tool according to this invention is particularly suitable for the finishing of soft workpieces, it is also well suited to the grinding of workpieces with a hard and/or straight surface.